Joule-thomson effect cooling system



July 11, 1961 SIMON 2,991,633

JOULE-THOMSON EFFECT COOLING SYSTEM Filed March 17, 1958 FPaHk/MS ZH,

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United States Patent 2,991,633 JOULE-THOMSON EFFECT COOLING SYSTEM FrankN. Simon, Bloomington, Minn, assignor to International Telephone andTelegraph Corporation Filed Mar. 17, 1958, Ser. No. 722,067 11 Claims.((31. 62-514) This invention relates to Joule-Thomson effect coolingapparatus and more particularly to a Joule-Thomson effect cooling systemproviding fast initial cool-down to a re duced temperature andsubsequent maintenance of such reduced temperature with minimum gasconsumption.

Joule-Thomson effect cooling devices are well known in the art and areemployed where it is desired to obtain extremely low temperatures;Joule-Thomson effect cooling devices are capable of producingtemperatures as low as l96 C. Such a device conventionally includes athin wall tube or jacket having a closed lower end and a low pressuregas discharge opening adjacent its other end, the jacket being formed ofsuitable material having good heat transfer properties, such asstainless steel. Entering the jacket is a small elongated capillary tubeextending downwardly, typically in a coiled coil configuration andterminating in a small nozzle. Gas, having a Joule-Thomson coefficientwhich is positive (ZNS, 2/15/5 8) at room temperature, such as nitrogen,is supplied under high pressure to the capillary tube and expandsthrough the nozzle. This expansion of the gas to the nozzle causesinitial cooling, and the gas then flows upwardly over the convolutionsof the tubing thus extracting further heat from the tubing in the natureof a heat exchanger, the gas being finally exhausted to the atmospherethrough the low pressure discharge opening of the jacket.

In installations in which size and Weight are not a factor and with alarge supply of gas available, the capillary tubing of the Joule-Thomsoneffect device is made sufficiently large to provide a sufiicientlyfast'gas flow so that initial cool-down to the desired temperature isaccomplished in the desired length of time, with the gas fiow thereafterbeing reduced by means of suitable valves in order to maintain thedesired reduced temperature. However, in certain self-contained systemsin which minimum size and weight are essential, it is necessary that thegas flow be small in order to limit the gas supply tanks or compressorto a correspondingly small size. For such small flows, however, theinitial cool-down time is substantially increased. This lengthenedcool-down time may not be of any particular disadvantage in certaininstallations, however there are other applications for Joule-Thomsonefiect devices in which it is desired that the initial cooldown time beas short as possible with a further requirement that the reducedtemperature obtained after the initial cool-down be maintained for asubstantial period of time. In such systems, with size and weight beingcritical, the use of' automatic devices such as thermally responsiblevalves to reduce the gas flow from that which will provide fast initialcool-down to a lower level to maintain the required temperature, isprohibited. It is thus seen that an apparently irreconcilable conflictin requirements is present, i.e., if a capillary tube is provided ofsufiicient size to provide a sufliciently fast gas flow to secure thedesired rapid temperature drop, continuance of this fast gas flow inorder to maintain the reduced temperature for the desired period of timewould require a gas supply tank of prohibitive size. On the other hand,if a capillary tube of smaller size is provided, thereby to permit theuse of a smaller gas storage tank, the initial cool-down time of thedevice is prohibitively long.

In accordance with the broader aspects of my invention therefore, Iprovide a Joule-Thomson effect cooling system having two gas conduitmeans connected respec- Patented July 11, 1961 tively to two gassupplying means. One of the gas conduit means is arranged forsubstantially faster gas flow than the other gas conduit means therebypro viding fast initial cool-down of the device to the desired reducedtemperature responsive to the faster gas flow, with maintenance of thereduced temperature thereafter being provided by the slower gas flowthrough the other gas conduit means. More specifically, I provide twoelongated tubes respectively in close proximity within an enclosingjacket, each of the tubes having a gas discharge opening at one endthereof adjacent the closed end of the jacket and having their otherends extending out of the jacket and respectively connected to two gasreservoir means for supplying gas at high pressure thereto. One of theelongated tubes is arranged for substantially faster gas flow than theother and the gas reservoir means connected to said one tube has a gascapacity to supply the one tube for a first predetermined period therebyto supply fast initial cool-down of the device to the desired reducedtemperature. The other gas reservoir means has a gas capacity sufficientto supply the other tube with the slower gas flow for a predeterminedperiod substantially longer than the initial cool-down period thereby tomaintain the reduced temperature responsive to the slower gas flow inthe other elongated tube. With this arrangement, both gas reservoirs maybe relatively small, one emptying in a relatively short period, i.e.,for example fifteen (15) seconds or less, to provide the fast initialcool-down, and the other emptying in a substantially longer period,i.e., for example, fifteen (15) minutes to one-half /2) hour, in orderto maintain the reduced temperature.

It is accordingly an object of my invention to provide an improvedJoule-Thomson effect cooling system.

Another object of my invention is to provide an improved Ioule-Thomsoneffect cooling system providing fast initial cool-down and maintenanceof the reduced temperature for a substantial period thereafter withminimum gas consumption.

A further object of my invention is to provide an improved Joule-Thomsoneffect cooling system in which fast gas flow is provided for a shortperiod to secure initial cool-down and slow gas flow is thereafterprovided for a substantially longer period to maintain the reducedtemperature, the system occupying minimum size and weight and notincorporating valve means or other control devices.

The above-mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent and the inventionitself will be best understood by reference to the following descriptionof an embodiment of the invention taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a side elevational view, partly in section and partly brokenaway, showing one embodiment of my improved Joule-Thomson effect coolingsystem;

FIG. 2 is a fragmentary cross-sectional view showing a modified form ofthe Joule-Thomson effect cooling device of FIG. 1;

FIG. 3 is a fragmentary cross-sectional View showing yet anothermodified form of my invention; and

FIG. 4 is a fragmentary view showing the actual configuration of thecoiled coil capillary tubes of the embodia ments of FIGS. 1, 2 and 3.

Referring now to FIG. 1, my improved Joule-Thomson effect coolingsystem, generally identified as 1, includes an elongated thin wall tubeor jacket 2 formed of material having good heat conduction properties,such as stainless steel, and having a closed end 3 and a low pressuregas discharge opening 4 adjacent its other end 5. Disposed within thejacket 2 is a central mandril 6 having a first elongated capillary tube7 wound thereon; the capillary tube 7 preferably has a coiled coilconfiguration as best shown in FIG. 4. Capillary tube 7 has a gasdischarge opening or nozzle 8 at its end 9 adjacent the closed end 3 ofthe jacket 2, and has its other end 9 extending out of the jacket 2, forexample through the low pressure gas discharge opening 4. End 9 ofcapillary tube 7 is connected to a high pressure gas supply tank 10 bymeans of line 11 for supplying a suitable gas, such as nitrogen, at highpressure thereto.

In accordance with my invention, I provide a second capillary tube 12wound over the first capillary tube 7 and also preferably having acoiled coil configuration, as shown in FIG. 4. The second capillary tube12 has a gas discharge opening 16 at its end 14 adjacent closed end 3 ofjacket 2 and has its other end 15 extending out of jacket 2, as throughlow pressure gas discharge opening 4. End 15 of the second capillarytube 12 is connected to a second gas supply tank 16 by a line 17 forsupplying a suitable gas, such as nitrogen, at high pressure thereto.

It will be seen that the second elongated capillary tube 12 has itsinside diameter and its gas discharge opening 13 substantially larger,respectively, than the inside diameter and gas discharge opening 8 ofthe first capillary tube 7, thereby providing substantially faster gasflow thereto. Thus, the second elongated capillary tube 12 may have aninside diameter of .040 inch and a gas discharge opening 13 .040 inch indiameter to provide a gas flow of 200 liters per minute with the tank 16supplying a suitable gas, such as nitrogen, under a pressure of 2,000pounds per square inch. With this fast rate of gas flow, the jacket 2should cool down to its low temperature of -196 C. in approximatelyfifteen (15) seconds and thus gas supply tank 16 need only have suchcapacity as to supply gas for such fifteen (15) second period; a gassupply tank 16 accommodating approximately one-half (V2) liter of gasshould therefore sufiice for this purpose. Once the device has beeninitially cooled down to the desired lower temperature, the l96 C. canbe maintained by a much slower gas flow. Therefore, the inner elongatedconvolute tube 7 may have an inside diameter of 0.010 inch and a gasdischarge opening 8 having a diameter of 0.010 inch to supply a fiow ofthree (3) liters per minute with gas supply tank 10 supplying thesuitable gas, again such as nitrogen, at 2,000 pounds per square inch.If it is desired that the reduced temperature be maintained for on theorder of fifteen (15) minutes, the volume of the tank 10 would be on theorder of threefourths liters.

It will be readily understood that the size of the gas discharge opening13 of the capillary tube 12 and the volume of gas supply tank 16 dependsupon the permissible duration of the initial cool-down period and thatthe volume of the other gas supply tank depends upon the required periodfor maintenance of the reduced temperature after the initial cool-downperiod. In any event, the gas supply tank 16 supplying the largercapillary tube 12 need only be of sufiicient size to supply gas duringthe initial cool down period; since the initial cooldown period will bevery short with the fast gas flow provided by the larger capillary tube12, the size of the gas supply tank 16 may nevertheless be relativelysmall with the other gas supply tank 10 supplying the smaller capillarytube 7 being also relatively small since the gas flow provided therebythrough the smaller capillary tube 7 is very slow compared with thatprovided by the larger capillary tube 12. It will be readily understoodthat the gas discharge through the gas discharge openings 8 and 13 ofthe capillary tubes 7 and 12 respectively fiows upwardly, as indicatedby the arrows 18 over the convolutions of the coiled coil tubes 7 and 12providing the heat exchanging action to secure the extremely cold lowertemperature, the gas finally being exhausted to the atmosphere throughthe low pressure gas discharge opening 4.

Referring now to FIGS. 2 and3, it will be seen that whereas in theembodiment of FIG. 1, the larger elongated capillary tube 12 is wound orcoiled over the smaller capillary tube 7, the two capillary tubes 7 and12 may be wound side by side as shown in FIG. 2, or with the smallercapillary tube 7 wound or coiled over the larger capillary tube 12 asshown in FIG. 3.

It will now be seen that I have provided an improved Joule-Thomsonelfect cooling system in which fast initial cool-down is providedtogether with subsequent maintenance of the reduced temperature for apredetermined additional period with minimum gas consumption and thusminimum size and weight of the accompanying gas supply tanks.

While 11 have described above the principles of my invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of my invention.

What is claimed is:

l. A Joule-Thomson effect cooling system comprising: a cooling devicehaving first and second elongated tubes each having a gas dischargeopening at one end thereof, an enclosure member having a closed end anda low pressure gas discharge opening adjacent the other end, said firstand second tubes being arranged in said enclosure with their gasdischarge ends adjacent said closed end and with their other endsextending out of said enclosure adjacent said other end thereof; andfirst and second gas storage tanks respectively connected to said otherends of said tubes for respectively supplying gas at high pressurethereto; said first tube gas discharge opening being substantiallylarger than said second tube gas discharge opening thereby providingsubstantially faster gas tfiow therethrough; said first gas storage tankhaving a gas capacity to supply said faster gas flow for a firstpredetermined relatively short period thereby to provide fast initialcool-down of said device to a reduced temperature; said second gasstorage tank having a gas capacity to supply the slower gas flow in saidsecond tube gas discharge opening for a predetermined periodsubstantially longer than said first period thereby to maintain saidreduced temperature.

2'. A Joule-Thomson effect cooling system comprising: a cooling devicehaving first and second elongated convolute tubes each having a gasdischarge opening at one end thereof, and a thin wall elongated jacketfomied of material having good heat transfer properties having a closedend and a low pressure gas discharge opening adjacent its other end,said first and second tubes being arranged respectively in closeproximity within said jacket with their gas discharge opening endsadjacent said closed end and with their other ends extending out of saidjacket adjacent said other end thereof; and first and second gas storagetanks respectively connected to said other ends of said tubes forrespectively supplying gas at high pressure thereto; said first tubehaving its inside diameter and gas discharge opening respectivelysubstantially larger than the inside diameter and gas discharge openingof said second tube thereby providing substantially faster gas flowtherethrough; said first gas storage tank having a gas capacity tosupply said faster gas flow for a first predetermined relatively shortperiod thereby to provide fast initial cool-down of said device to areduced temperature; said second gas storage tank having a gas capacityto supply the slower gas flow in said second tube gas discharge openingfor a predetermined period substantially longer than said first periodthereby to maintain said reduced temperature.

3. A Joule-Thomson eliect cooling system comprising: a cooling devicehaving a first elongated coiled tube with a gas discharge opening at oneend thereof, a second elongated coiled tube arranged in engagement withsaid first tube and having a gas discharge opening at one end thereof,and a thin wall elongated jacket formed of material having good heattransfer properties and having a closed end and a low pressure gasdischarge opening adjacent its other end, said first and second tubesbeing arranged in said jacket with their gas discharge opening endsadjacent said closed end and with their other ends extending out of saidjacket adjacent said other end thereof; and first and second gas storagetanks respectively connected to said other ends of said tubes forrespectively supplying gas at high pressure thereto; said first tubehaving its inside diameter and gas discharge opening respectivelysubstantially larger than the inside diameter and gas discharge openingof said second tube thereby providing substantially faster gas flowtherethrough; said. first gas storage tank having a gas capacity tosupply said faster gas flow for a first predetermined relatively shortperiod thereby to provide fast initial cool-down of said device to areduced temperature; said second gas storage tank having a gas capacityto supply the slower gas flow in said second tube gas discharge openingfor a predetermined period substantially longer than said first periodthereby to maintain said reduced temperature.

4. A Joule-Thomson effect cooling system comprising: a cooling devicehaving first and second elongated tubes coiled on a common mandril andeach having a gas discharge opening at one end, and a thin wallelongated jacket formed of material having good heat transfer propertiesand having a closed end and a low pressure gas discharge openingadjacent its other end, said mandril with said first and second tubescoiled thereon being arranged in said jacket with said gas dischargeends of said tubes being adjacent said closed end and with their otherends extending out of said jacket adjacent said other end thereof; andfirst and second gas storage tanks respectively connected to said otherends of said tubes for respectively supplying gas at high pressurethereto; said first tube having its inside diameter and gas dischargeopening respectively substantially larger than the inside diameter andgas discharge opening of said second tube thereby providingsubstantially faster gas fiow therethrough; said first gas storage tankhaving a gas capacity to supply said faster gas flow for a firstpredetermined relatively short period thereby to provide fast initialcool-down of said device to a reduced temperature; said second gasstorage tank having a gas capacity to supply the slower gas flow in saidsecond tube gas discharge opening for a predetermined periodsubstantially longer than said first period thereby to maintain saidreduced temperature.

5. A Joule-Thomson effect cooling system comprising: a cooling devicehaving a first elongated coiled tube coiled on a mandril and having agas discharge opening at one end thereof, a second elongated coiled tubecoiled over said first tube and having a gas discharge opening adjacentone end thereof, and a thin Wall jacket formed of material having goodheat transfer properties and having a closed end and a low pressure gasdischarge opening adjacent its other end, said mandril with said firstand second tubes coiled thereon being arranged in said jacket with saidgas discharge ends of said tubes being adjacent said closed end and withtheir other ends extending out of said jacket adjacent said other endthereof; and first and second gas storage tanks respectively connectedto said other ends of said tubes for respectively supplying gas at highpressure thereto; said first tube having its inside diameter and gasdischarge opening respectively substantially larger than the insidediameter and gas discharge opening of said second tube thereby providingsubstantially faster gas flow therethrough; said first gas storage tankhaving a gas capacity to supply said faster gas flow for a firstpredetermined relatively short period thereby to provide fast initialcool-down of said device to a reduced temperature; said second gasstorage tank having a gas capacity to supply the slower gas flow in saidsecond tube gas discharge opening for a predetermined periodsubstantially longer than said first period thereby to maintain saidreduced temperature.

6. A Joule-Thomson effect cooling system comprising: a cooling devicehaving a first elongated coiled tube coiled on a mandril and having agas discharge opening at one end thereof, a second elongated coiled tubecoiled over said first tube and having a gas discharge opening adjacentone end thereof, and a thin wall jacket formed of material having goodheat transfer properties and having a closed end and a low pressure gasdischarge opening adjacent its other end, said mandril with said firstand second tubes coiled thereon being arranged in said jacket with saidgas discharge ends of said tubes being adjacent said closed end and withtheir other ends extending out of said jacket adjacent said other endthereof; and first and second gas storage tanks respectively connectedto said other ends of said tubes for respectively supplying gas at highpressure thereto; said second tube having its inside diameter and gasdischarge opening respectively substantially larger than the insidediameter and gas discharge opening of said first tube thereby providingsubstantially faster gas flow therethrough; said second gas storage tankhaving a gas capacity to supply said faster gas flow in said second tubedischarge opening for a first predetermined relatively short periodthereby to provide fast initial cool-down of said device to a reducedtemperature; said first gas storage tank having a gas capacity to supplythe slower gas flow in said first tube gas discharge opening for apredetermined period substantially longer than said first period therebyto maintain said reduced temperature.

7. A Joule-Thomson effect cooling system comprising: a cooling devicehaving first and second elongated coiled tubes coiled side-by-side on acommon mandril and each having a gas discharge opening at one end, and athin Wall elongated jacket formed of material having good heat transferproperties and having a closed end and a low pressure gas dischargeopening adjacent its other end, said mandril with said first and secondtubes coiled thereon being arranged in said jacket with said gasdischarge ends of said tubes being adjacent said closed end and Withtheir other ends extending out of said jacket adjacent said other endthereof; and first and second gas storage tanks respectively connectedto said other ends of said tubes for respectively supplying gas at highpressure thereto; said first tube having its inside diameter and gasdischarge opening respectively larger than the inside diameter and gasdischarge opening of said second tube thereby providing substantiallyfaster gas flow therethrough; said first gas storage tank having a gascapacity to supply said faster gas flow in said first tube gas dischargeopening for a first predetermined relatively short period thereby toprovide fast initial cool-down of said device to a reduced temperature;said second gas storage tank having a gas capacity to supply the slowergas How in said second tube gas discharge opening for a predeterminedperiod substantially longer than said first period thereby to maintainsaid reduced temperature.

8. In a Joule-Thomson eifect cooling device having an enclosure memberwith an open end and a closed end: first and second elongated convolutetubes respectively in engagement substantially throughout their lengthsand respectively having gas discharge openings at one end and havingtheir other ends adapted respectively to be connected to first andsecond high pressure gas supply means, said tubes being adapted to bedisposed in said enclosure member with their gas discharge openingsadjacent said closed end thereof, one of said tubes having a gasdischarge opening substantially larger than the gas discharge opening ofthe other tube thereby providing substantially faster gas flowtherethrough.

9. In a J oule-Thomson effect cooling device having an enclosure memberwith an open end and a closed end: first and second elongated coiledtubes coiled on a common mandril and respectively having gas dischargeopenings at one end and having their other ends adapted respectively tobe connected to first and second high pressure gas supply means, saidtubes being adapted to be disposed in said enclosure member with theirgas. discharge openings adjacent said'closed end thereof, one of saidtubes having its inside diameter and gas discharge openings respectivelysubstantially larger than the inside diameter and gas discharge openingof the other tube thereby providing substantially faster gas flowtherethrough.

10. In a Joule-Thomson effect cooling device having an enclosure memberwith an open end and a closed end: a first elongated coiled tube coiledon a mandril and having a gas discharge opening at one end; and a secondelongated coiled tube coiled over said first tube and haviug a gasdischarge opening at one end; said tubes having their other ends adaptedrespectively to be connected to first and second high pressure gassupply means, said tubes being adapted to be disposed in said enclosuremember with their gas discharge openings adjacent said closed endthereof, one of said tubes having its inside diameter and gas dischargeopenings respectively substantially larger than the inside diameter andgas discharge opening of the other tube thereby providing substantiallyfaster gas flow therethrough.

11. In a Joule-Thomson effect cooling device having an enclosure memberwith an open end and a closed end:

first and second elongated coiled tubes coiled side-by-side on a commonmandril and respectively having gas dischargeopenings at one end andhaving their other ends diameter and gas discharge opening of the othertube thereby providing substantially faster gas flow therethrough.

References Cited in the file of this patent UNITED STATES PATENTS1,471,832 Davis Oct. 23, 1923 1,968,518 Fraser July 31, 1934 2,159,251Brizzloara May 23, 1939 2,487,863 Garretson Nov. 15, 1949 2,502,184Thayer Mar. 28, 1950 2,509,034 Claitor May 23, 1950 2,725,722 AhlstrandDec. 6, 1955 2,763,138 Tsunoda Sept. 18, 1956 2,909,903 Zimmermann Oct.27, 1959 2,913,609 Lennard Nov. 17, 1959

